Known arrangements for alerting a vehicle driver to potential danger have utilized lights and/or buzzers located in the vehicle instrument panel. In addition, for collision avoidance systems, a heads-up display has been proposed to display threat symbols for the driver to see while driving.
However, audible tones or warning lights have not proven to be completely satisfactory because they are ineffective as warning devices for high threat real-time situations. Warning lights on an instrument panel will not be seen unless the operator looks at them, which inadvertently causes the driver's attention to be diverted from the road. Audible tones (buzzers, etc) tend to only confuse the driver since the tones do not inherently provide a context for the tone unless the driver is provided with considerable training. For example, a driver can not necessarily determine the possible source or type of danger simply from hearing the tone. In addition, in very complex situations, humans tend to not notice these tone sounds at all, and if anything, the noise only adds to the level of confusion in the situation.
Heads-up displays also suffer from the drawback that a driver's attention can be inadvertently diverted from the road in order to concentrate on a particular display region of the windshield. For situations such as a possible collision, the warning information must be immediately recognized by the operator to be effective. Requiring the operator to physically look to the display at a regular interval to see if a warning is present reduces the effectiveness of the warning system. Also for situations where an operator is less attentive than desired, such as driving when sleepy or while under the influence of alcohol, these visual monitor-type warnings are completely ineffective. In addition, many drivers, particularly older drivers with poor vision, find heads-up displays very awkward and difficult to use.
Faced with a potential crash, the driver must act quickly and decisively to take corrective action to avoid the crash. Under these circumstances, the typical driver does not normally have time to think about what to do or to comprehend messages from a typical display system. Instead, the operator needs intuitive cues which evoke the correct automatic driver reactions. The main disadvantage of prior art collision warning systems is that they do not provide such cues.